2010 II 12 Volt Battery Dead After 17 Days of Parking

Disclaimer: I am not all that e-smart. Sometimes with sheer persistence,
you get lucky... with a lot of help from your friends.

In addition to the small 12v battery, there is another source of stored
electrical energy in the Gen II at least: an ultra-cap (?) in the brake
system. IIRC, it is a paper-back book sized black box mounted vertically
next to the 12v battery. I don't know what voltage it runs on.

Given the relatively small power needs and short time required to boot
the appropriate cpu(s) to get the HV battery switched on and powering
the DC/DC converter, would it be worth considering finding/hacking a
way to momentarily tap into the ultra/cap?

Yeah, great caution needed as it is an essential safety system.

Well, I've been wandering through various doc and can't find
anything about this "short pin". That doesn't mean it's not
there, but if it's for real it's mighty obscure as far as
being something the techs need to routinely deal with.
.
Gone are the days, perhaps, of pulling the "dome" fuse which
seems to be the main keepalive in the second-gen. But I'm not
100% sure that kills everything there either.
.
Maybe the third-gen needs one or both of ECU-B2 [13] and ECU-B
[30] pulled in the underhood block, as those seem to supply most
of the battery power to the smartkey/immobilizer units.
.
Important note: you generally cannot measure very small currents
with a clamp-on, you need to actually break a main connection
and leave a real milliammeter connected across the gap so it's
in series with the rest of the car. And that needs to be done
with nothing powered up, no courtesy lights on, etc -- if you
open the drivers door then a whole forest of ECUs kick on at
least temporarily, the brake accumulator might try to run ...
so one does need to be careful to let the car come down to its
absolute baseline before assuming anything about current drawn.
.
I did find this in one of the service pages, no clue if it's
relevant:

Code:

3. ELECTRICAL KEY CANCEL

The electrical key cancel operation disables the following
functions: 
    * Entry Unlock/Lock
    * Entry Hybrid Vehicle Control System Start
    * Entry System Back Door Open Function*
      *: w/ Entry System Back Door Open Function
    * Electrical Key Lock-in Prevention
    * Warning

(a) The operation procedure is as follows:

Precondition:  Power switch off, driver door closed and unlocked.

(1) Push the unlock switch of the key once.

(2) Open the driver door within 5 seconds.

(3) Push the unlock switch of the key twice within 5 seconds.

(4) Close and open the driver door twice within 30 seconds.

(Driver door: Close --> Open --> Close --> Open)

(5) Push the unlock switch of the key twice within 5 seconds.

(6) Close and open the driver door within 30 seconds.

(Driver door: Close --> Open)

(7) Close the driver door within 5 seconds.

When electrical key cancel is activated, the wireless door lock
buzzer sounds twice.

To return to the original condition, perform the procedure again.
When the original condition is returned, the wireless door lock
buzzer sounds once.

.
Someone wanna go try that and see what still works or not?
.
_H*

Tumbleweed said:

"The alternative would be just to unhook the 12V battery and lose all the radio settings etc. I wouldn't mind that but I'm not sure if the backup beeper to 1 beep and the seat belt beeper to off settings would be lost as well? Anybody know?"

I'd sure like to know about this as well, before I go disconnecting the bat!

I just went to the garage and tried this. It appears that it completely turns off the SKS system. You can still use the key fob buttons to lock and unlock the car. This might be the solution for the battery drain over a period of time. It would still be much nicer to have a button like I had in my 07.

Check p.543 of your manual; there's a pretty slick covered jump (post? terminal?) in the underhood fuse box. How to jump is illustrated.
A similar jump post is near your 12V. battery.

The manual discusses discharge-over-time of the 201 volt hybrid battery. I don't recall similar for your 12V battery. I think your dealer is confused.

tiztim,

Hi.

My earlier post identified a typically unknown, or simply overlooked
source of stored electrical energy for consideration for a source of
short-term, emergency-only power to overcome a dead 12v battery.
Mention of the HV battery was solely to acknowledge the power path
that would need to be restored.

Of the five dealers I have visited for routine service from Maine to
Florida, I can't see any of the personel, Sales Persons, Service
Writers, or Technicians, engaging in a discussion like this... ever.

It is far more likely that they would try to sell me a Chevrolet Volt.

FYI- Jump starting the Prius:
I returned from a trip last Thursday (09/17/2009) and found the 12V battery dead on my 2008 Gen II Prius. My fault, I left map lights on. I found someone with Jumper cables, opened the hood, removed the covers from the fuse box and +12V contact point. Surprise, it is ressesed in a small cavity and ordinary jumper cables can't touch it. We had to clip the cable to a screw driver and hold the blade against the contact. Not a good soulution. I am going to make a small extension to screw on the +12 contact and carry it in the glove box in the event this happens again. BTW, once the car is booted up it will be charging the 12V battery even if the engine is not running.

Leave the car in "ready" mode.

With system left in "ready", the car doors will not lock from the outside using the touch sensor nor the remote button: You have to lock and unlock the doors using the manual key. Engine will start when battery gets low.

Kidding.

I would say if you need to park the car for that period of time in public, get one of those jump start battery things and then you can hook it up to the jump start terminals. Or just buy another battery of roughly the same size to jump start it. You only need to hook up the 2nd battery and wait 5 minutes or so to make sure the car boots up. Then you should be fine. If you park the car at a home location, you could put a trickle charger on it while your gone.

My Owner's Manual states, "As the gasoline engine or regenerative brake charges the hybrid battery (traction battery), the battery does not need to be charged from an outside source. However, if the vehicle is left parked for a long time the hybrid battery will slowly discharge. For this reason, be sure to drive the vehicle at least once every several months for at least 30 minutes or 10 miles (16 km)." (p. 30) This seems to be saying that the battery should hold a charge for at least one month, if not longer. It certainly doesn't seem consistent with the position that the battery will drain in 10 days.

Different batteries:
1. Traction about 200 volts
2. The "accessory" 12-volt battery, charged by the DC-to-DC converter.

Maybe a 100 to 200 v DC in to 12v DC out (with a diode), trickle charger, on constantly, would do the trick?

How many amp-hours is the 12v battery?

The Tracton battery (80% t0 40%) is only 0.5 kWh, or 500 Wh, or 40 amps at 12v for one hour, thus the energy of a 40 ah, 12v battery.

Maybe jumpering another charged "big" 12v battery in parallel with the "small" OEM 12v, just when the car is being "abandoned"?

DavidA; where does it say it automatically shut off after 3 days?

I cannot find it

I have had my Prius IV for about 10 dayds now and I'm worried about this "Battery Issue."

On page 49 of the Owners Manual:

Battery-saving function

In the following circumstances, the entry function is disabled in order to prevent the vehicle battery from discharging and electronic key battery from depleting.
l When the entry function has not been used for 5 days or more
l When the electronic key has been left within approximately 6 ft. (2 m) of the vehicle for 10 minutes or more
l If the entry function has not been used for 9 days or more, the vehicle cannot be unlocked by a door other than the driver’s door. To unlock the vehicle, grip the driver’s door handle or use the wireless remote control or the mechanical key.

The system will resume operation when...
l The vehicle is locked touching the door handle lock sensor area.
l The vehicle is locked/unlocked using the wireless remote control function (→P. 63) or the mechanical key. (→P. 541)

An Alarm System will continue to use current, presumably from the 12v battery, right?

Has anybody measured the current drain from the 12v battery when the car is off?

Can the 2010 Prius III EVER be unlocked by a door other than the driver door?
If so, how, please?

The same manual is used for all of the models. Some have SKS for both front doors and the hatch, while cheaper models have SKS on only the driver's door.

Tom

My solution is to just buy a portable jump starter - one that you charge up at home via power outlet and just keep it with you. Hook up the + and - to the proper places on the prius, and start. No biggie if the Prius 12v is dead.

Not so far as I know. I am perfectly willing to do so except for one thing, when I unhook it to put an Amp meter in series with one of the terminals will it reset my cusomizable options. I have the backup beeper set to one beep and the seatbelt beeper turned off. I don't want to have to go back to the dealer and have them reset again. They did it free the first time after some discussion, if I go back they will try to charge me. At this point we don't know if those options are reset when you loose 12V DC or not, so I'll wait and see.